!function(win) {
  function resize() {
      var domWidth = domEle.getBoundingClientRect().width;
      /*获取设备宽度-物理像素值*/
      if(domWidth / v > 540){
          domWidth = 540 * v;
      }
      win.rem = domWidth / 7.5;
      /*windows的rem值*/
      domEle.style.fontSize = win.rem + "px";
      /*html:font-size=150px*/
  }
  var v, initial_scale, timeCode, dom = win.document, domEle = dom.documentElement,
      viewport = dom.querySelector('meta[name="viewport"]'),
      flexible = dom.querySelector('meta[name="flexible"]');
  if (viewport) {
      //viewport：<meta name="viewport"content="initial-scale=0.5, minimum-scale=0.5, maximum-scale=0.5,user-scalable=no,minimal-ui"/>
      var o = viewport.getAttribute("content").match(/initial\-scale=(["']?)([\d\.]+)\1?/);
      if(o){
          initial_scale = parseFloat(o[2]);
          v = parseInt(1 / initial_scale);
      }
  } else {
      if (flexible) {
          var o = flexible.getAttribute("content").match(/initial\-dpr=(["']?)([\d\.]+)\1?/);
          if(o){
              v = parseFloat(o[2]);
              initial_scale = parseFloat((1 / v).toFixed(2))
          }
      }
  }
  if (!v && !initial_scale) {
      var n = (win.navigator.appVersion.match(/android/gi), win.navigator.appVersion.match(/iphone/gi));
      v = win.devicePixelRatio;
      v = n ? v >= 3 ? 3 : v >= 2 ? 2 : 1 : 1, initial_scale = 1 / v
  }
  //没有viewport标签的情况下
  if (domEle.setAttribute("data-dpr", v), !viewport) {
      if (viewport = dom.createElement("meta"), viewport.setAttribute("name", "viewport"), viewport.setAttribute("content", "initial-scale=" + initial_scale + ", maximum-scale=" + initial_scale + ", minimum-scale=" + initial_scale + ", user-scalable=no"), domEle.firstElementChild) {
          domEle.firstElementChild.appendChild(viewport)
      } else {
          var m = dom.createElement("div");
          m.appendChild(viewport), dom.write(m.innerHTML)
      }
  }
  win.dpr = v;
  win.addEventListener("resize", function() {
      clearTimeout(timeCode), timeCode = setTimeout(resize, 300)
  }, false);
  win.addEventListener("pageshow", function(b) {
      b.persisted && (clearTimeout(timeCode), timeCode = setTimeout(resize, 300))
  }, false);
  resize();
}(window);